The present application is directed to duplexer assemblies and, more particularly, to structures and method for improving the reliability of duplexer assemblies.
Ceramic duplexers typically are used in various electronic communication devices. In particular, monolithic ceramic duplexers often are used in cellular telephone circuits and the like to facilitate the transmission and receipt of communication signals.
Ceramic duplexers may include a multipole shaped ceramic piece adapted to connect (e.g., with soft solder or the like) to various metal traces on a printed circuit board. Such ceramic duplexers often are relatively large as compared to the size of the printed circuit board. For example, a ceramic duplexer may be about 1.5 inches long, about 0.5 inches wide and about 0.25 inches tall. The connection thickness between the duplexer and the printed circuit board may be in the range of about 1 to about 5 mils, as commonly obtained using commercial electronic assembly methods.
Typically, there is a significantly large mismatch between the coefficients of thermal expansion of the printed circuit board and the ceramic duplexer. For example, an epoxy/glass printed circuit board may have a coefficient of thermal expansion of about 16 parts per million per ° C. (“ppm/° C.”) and a ceramic duplexer may have a coefficient of thermal expansion of about 5 ppm/° C.
Accordingly, due to the significant mismatch between the coefficients of thermal expansion of the printed circuit board and the ceramic duplexer, as well as the relatively large size of the duplexer, the connection between the duplexer and the printed circuit board is prone to failure. In particular, the joint connecting the duplexer to the traces on the printed circuit board is prone to cracking when subjected to thermal cycling in the range of about −40° C. to about 85° C.
Attempts to address the connection failures by increasing the surface area of the duplexer/circuit board connection (e.g., increasing the surface area of the solder joint) have failed to remedy the problem. In some attempts, increasing the surface area of the connection resulted in a transfer of the stress generated by the coefficient of thermal expansion mismatch to the duplexer, thereby cracking the duplexer.
Accordingly, there is a need for an apparatus and method for connecting a duplexer to a circuit board such that the duplexer assembly is capable of withstanding the stresses typically associated with thermal cycling.